Also, the methane concentration in surface waters was lower than that in near-bottom waters at most sites, suggesting sediment methanogens are a likely source of methane. In the estuarine mixing zone, significantly high methane concentrations existed with the presence of salt-tolerant methanogens (e.g., Methanomicrobiaceae, Methanocella, Methanosaeta Methanobacterium and ) and methanotrophs (e.g., Methylocystis Methylococcaceae and ), which were found in brackish habitats. Furthermore, a number of methanotrophic OTUs (from pmoA gene sequence data) had specific positive correlations with methanogenic OTUs (from mcrA gene sequence data), and some of these methanogenic OTUs were correlated with concentrations of particulate organic carbon (POC). The results indicate that methanotrophs and methanogens may be intimately linked in methane metabolism attached with particles in estuarine waters.

Chen, X., Wu, D., Huang, X., Lv, F., Brenner, M., Jin, H., Chen, F., 2020. Vegetation response in subtropical southwest China to rapid climate change during the Younger Dryas. Earth-Science Reviews 201, 103080.

http://www.sciencedirect.com/science/article/pii/S0012825219306142 Investigations of past biotic responses to rapid climate shifts are useful for developing biological scenarios that may result from future climate change. In this context, the Younger Dryas (YD) cold climatic reversal (~12,800 - 11,500 cal yr BP), and the resulting vegetation response, is of considerable interest. In this study, we conducted pollen and grain-size analyses of a section spanning the interval of 17,600 - 8500 cal yr BP in a sediment core from Xingyun Lake, in Yunnan Province, southwest China. At the same time, the other 44 paleovegetation sites from Yunnan Plateau and elsewhere in China were reviewed. Our aims were to investigate the vegetation responses to climate changes during the YDand to integrate them with climate simulation results. During the YD climatic reversal, mean annual temperatures in Yunnan were ~1.5 - 2.4 °C colder than today. The vegetation response to the cooling during the YD was characterized by downward shifts in the Abies Picea Pinus elevation of vegetation zones. Notably, only a relatively small proportion of taxa, i.e., , , , Quercus Quercus (E), and Poaceae, were climatically sensitive during the YD, and changes in spring temperature were a major factor on the vegetation dynamics. In addition, there was a time lag in the vegetation response to the YDevent in the Yunnan Plateau. Consistent with other records from China, the YD climatic reversal only caused a change in vegetation composition rather than vegetation type succession. Notably, there was a latitudinal gradient in the magnitude of the YD cold event in China and in the resulting vegetation response. Changes in both temperature and precipitation were responsible for the vegetation changes at mid-to- high-latitudes, whereas the vegetation dynamics at low latitudes were determined largely by changes in spring temperature.

Chen, X., Zhu, L., Cui, C., Zhu, Y., Zhou, Z., Qi, F., 2020. In situ atmospheric pressure photoionization mass spectrometric monitoring of initial pyrolysis products of biomass in real time. Analytical Chemistry 92, 603- 606.

https://doi.org/10.1021/acs.analchem.9b05200 Knowledge on the initial and intermediate pyrolysis products of biomass is essential for the mechanistic investigation of biomass pyrolysis and further optimization of upgrading processes. The conventional method can only detect the final products, which do not resemble the initial or intermediate pyrolysis products. Here, we introduce a direct orifice sampling combined with atmospheric pressure photoionization mass spectrometry (APPI-MS) for in situ online analysis of the evolved volatile initial products from the pyrolysis of biomass. Pyrolysis experiments of both dimeric model compound (guaiacylglycerol- β -guaiacyl ether, GGGE) and poplar wood were carried out to validate the generality of the method. Generally, secondary reactions can be reduced by shortening the distance between the sample and sampling orifice. Large molecular-weight initial products up to trimers were detected during the pyrolysis of poplar wood, and no initial products larger than trimers were detected. It is inferred that in situ APPI immediately after sample extraction ensures efficient and effective product detection. Furthermore, the present work offers a promising feasible method for online tracing of reaction intermediates not only in pyrolysis but also in various reactive processes (e.g., catalytic reaction, oxidation) under operando conditions.